Transceiver circuit and method for operating a transceiver circuit

ABSTRACT

Embodiments of transceiver circuits and methods for operating a transceiver circuit are described. In one embodiment, a transceiver circuit includes a feedback loop connected to a bus and a control circuit connected to the bus. The feedback loop includes a tunable low-pass filter. The control circuit is configured to detect a radio frequency (RF) disturbance on the bus and control the bandwidth of the tunable low-pass filter in response to detection of the RF disturbance on the bus. Other embodiments are also described.

Embodiments of the invention relate generally to electrical circuits andmethods for operating electrical circuits, and, more particularly, tocommunications circuits and methods for operating communicationscircuits.

Transceiver circuits are important components in a bus-basedcommunications network. To insure proper transmission and reception ofdata through a communications bus, a transceiver circuit needs toachieve low electromagnetic emission (EME) during data transmission. Inaddition, a transceiver circuit needs to be robust against radiofrequency (RF) electromagnetic disturbance or interference.

In a typical open-loop transceiver circuit, low EME is usually achievedby means of waveshaping that controls the transition time and theamplitude of an output voltage. However, a typical open-loop transceivercircuit is not able to compensate for impedance variations on acommunications bus. Consequently, the output voltage of a typicalopen-loop transceiver circuit changes with the bus impedance, whichaffects the EME of the transceiver circuit.

Electromagnetic disturbance or interference on a communications bus candegrade the performance of transceiver circuits connected to thecommunications bus. Yet, data must be properly transmitted and receivedvia the communications bus, even in the presence of RF disturbance.However, in a typical open-loop transceiver circuit, the voltage on acommunications bus exhibits direct current (DC) shift, which can lead tobit errors in the transceiver circuit.

Embodiments of transceiver circuits and methods for operating atransceiver circuit are described. In one embodiment, a transceivercircuit includes a feedback loop connected to a bus and a controlcircuit connected to the bus. The feedback loop includes a tunablelow-pass filter. The control circuit is configured to detect an RFdisturbance on the bus and control the bandwidth of the tunable low-passfilter in response to detection of the RF disturbance on the bus. Thetransceiver circuit can adaptively adjust the tunable low-pass filterbased on continuous-time feedback from the communications bus to protectthe feedback loop from high-frequency (HF) disturbances. Otherembodiments are also described.

In one embodiment, a method for operating a transceiver circuit involvesdetecting an RF disturbance on a bus connected to the transceivercircuit and controlling the bandwidth of a tunable low-pass filter ofthe transceiver circuit in response to detection of the RF disturbanceon the bus.

In one embodiment, a transceiver circuit includes a receiver section anda transmitter section. The transmitter section includes a feedback loopconnected to a single-ended bus and a control circuit connected to thesingle-ended bus. The feedback loop includes a tunable low-pass filterand an error amplifier. The control circuit is configured to detect anRF disturbance on the single-ended bus and control the bandwidth of thetunable low-pass filter in response to detection of the RF disturbanceon the single-ended bus.

Other aspects and advantages of embodiments of the present inventionwill become apparent from the following detailed description, taken inconjunction with the accompanying drawings, depicted by way of exampleof the principles of the invention.

FIG. 1 is a schematic block diagram of a communications system inaccordance with an embodiment of the invention.

FIG. 2 depicts a communications system that is compatible with the LocalInterconnect Network (LIN) protocol.

FIG. 3 depicts an embodiment of the transceiver circuit of FIG. 1 thatis compatible with the LIN protocol.

FIG. 4 depicts an embodiment of the transceiver circuit depicted in FIG.3 that includes a continuous-time bus feedback loop.

FIG. 5 is a graph of tuning signal versus the amplitude of ahigh-frequency (HF) LIN bus disturbance of the transceiver circuitdepicted in FIG. 4.

FIG. 6 is a graph of a signal voltage that illustrates transmissions ofbits from the transceiver circuit depicted in FIG. 4 under differentbus-load conditions.

FIG. 7 is a graph of an EM Immunity simulation of the transceivercircuit depicted in FIG. 4.

FIG. 8 is a graph representing the bit time of a received signal of thetransceiver circuit depicted in FIG. 4 during an EM Immunity simulation.

FIG. 9 is a process flow diagram of a method for operating a transceivercircuit in accordance with an embodiment of the invention.

FIG. 10 is a process flow diagram of a method for operating atransceiver circuit in accordance with another embodiment of theinvention.

Throughout the description, similar reference numbers may be used toidentify similar elements.

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure, but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

The described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by this detaileddescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment. Rather, language referring to the features andadvantages is understood to mean that a specific feature, advantage, orcharacteristic described in connection with an embodiment is included inat least one embodiment. Thus, discussions of the features andadvantages, and similar language, throughout this specification may, butdo not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment. Thus, the phrases “inone embodiment,” “in an embodiment,” and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment.

FIG. 1 is a schematic block diagram of a communications system 100 inaccordance with an embodiment of the invention. In the embodimentdepicted in FIG. 1, the communications system includes a communicationdevice 102, which includes a transceiver circuit 104, and acommunications network 106. The communications system can be used tofacilitate communications between communication devices/nodes. In someembodiments, the communications system is used in a vehicle. Examples ofa vehicle may include, without limitation, an automobile, a bus, atrain, an industrial or agricultural vehicle, a ship, or an aircraft.Although the communications system is shown in FIG. 1 as includingcertain components, in some embodiments, the communications systemincludes less or more components to implement less or morefunctionalities.

The transceiver circuit 104 of the communication device 102 isconfigured to communicate with other communication devices/nodes. In theembodiment depicted in FIG. 1, the transceiver circuit is configured tocommunicate with the communications network 106 through a communicationsbus 108. The communications bus can be any dubitable type ofcommunications bus. In some embodiments, the communications bus is asingle-ended communications bus. In the single-ended communications bus,signals are carried by the voltage of a single wire. Compared to adifferential communications bus, in which the same information istransmitted with opposite voltages simultaneously through two sets ofwires, the single-ended communications bus can be less expensive andeasier to implement. For example, compared to differentialcommunications buses, single-ended communications buses use fewer wires,allowing the reduction of harness (e.g., electrical wirings) in avehicle. In some embodiments, the single-ended communications bus is abus that is compatible with the Local Interconnect Network (LIN)protocol, which is a serial communication protocol suitable for low costand high performance in-vehicle network (IVN). In some embodiments, thecommunications bus is a one wire of a differential bus. The transceivercircuit is also configured to communicate with a microcontroller 110through input/output (I/O) terminals 112-1, 112-2. The microcontrollermay be connected to a sensor/actuator device and to control thesensor/actuator device or gather information from the sensor/actuatordevice. The sensor/actuator device can be a sensor that is used tocollect operating parameters in a vehicle and/or an actuator, such as acontroller that is used to control a certain function/component of avehicle. In some embodiments, instead of the microcontroller, thecommunications system 100 includes other device that communicates withthe transceiver circuit and performs a different function.

In the embodiment depicted in FIG. 1, the transceiver circuit 104includes a receiver section, “Rx,” 130 and a transmitter section, “Tx,”140. The receiver section is connected to the I/O terminal 112-2, fromwhich a data signal, “RxD,” is transmitted to the microcontroller 110.In some embodiments, the transmitter section includes a feedback loop114, which includes a tunable low-pass filter 116, and a control circuit118, and another transmitter component 142, such as an amplifier deviceand/or a waveshaping device. The transmitter section is connected to theI/O terminal 112-1, from which a data signal, “TxD,” is received fromthe microcontroller. The feedback loop and the control circuit areconnected to the communications bus 108. The control circuit isconfigured to detect an RF disturbance on the bus and control thebandwidth of the tunable low-pass filter in response to detection of theRF disturbance on the communications bus. In an embodiment, thetransceiver circuit adaptively adjusts the tunable low-pass filter basedon a continuous-time feedback from the communications bus to protect thefeedback loop from high-frequency (HF) disturbances. The transceivercircuit can achieve low electromagnetic (EM) emission and high EMimmunity. Specifically, the transceiver circuit can compensate loadvariations of the communications bus, which allows optimum waveshaping,therefore resulting in low EME. In addition, the transceiver circuit canachieve high EM immunity by changing the bandwidth of the tunablelow-pass filter based on the amplitude of high-frequency (HF)disturbance detected on the bus.

The communications network 106 of the communications system 100 isconfigured to receive data from the communication device 102 and totransmit data to the communication device. In the embodiment depicted inFIG. 1, the communications network is configured to communicate with thetransceiver circuit 104 through the communications bus 108.

In some embodiments, the communications system 100 is part of a LocalInterconnect Network (LIN). In these embodiments, the communications bus108 is a LIN bus and the transceiver circuit 104 is compatible with theLIN protocol, e.g., the LIN Specification 2.2.A. Compared todifferential IVN protocols, e.g. CAN or FlexRay, a LIN bus is asingle-ended bus, thereby allowing the reduction of electrical wiringsin a vehicle.

FIG. 2 depicts a communications system that is compatible with the LINprotocol. In the embodiment depicted in FIG. 2, a LIN communicationssystem 200 includes one or more slave nodes 202 and a master node 222,which acts as a control unit for the slave nodes. The slave nodes andthe master node are connected to a LIN bus 208. Each of the slave nodesincludes a transceiver circuit 204 and a slave module 206 that cancommunicate with a corresponding microcontroller or other device usingthe corresponding transceiver circuit. Each transceiver circuit 204 maybe similar to or the same as the transceiver circuit 104. The masternode includes a transceiver circuit 224 and a master module 226 that caninitiate communications between the master device and a correspondingslave device through the LIN bus. The transceiver circuit 224 may besimilar to or the same as the transceiver circuit 104.

FIG. 3 depicts an embodiment of the transceiver circuit 104 of FIG. 1that is compatible with the LIN protocol. In the embodiment depicted inFIG. 3, a transceiver circuit, “LIN TRx,” 304 includes a receiversection, “Rx,” 330 and a transmitter section, “Tx,” 340. The transceivercircuit depicted in FIG. 3 is one possible embodiment of the transceivercircuit depicted in FIG. 1. However, the transceiver circuit depicted inFIG. 1 is not limited to the embodiment shown in FIG. 3.

The receiver section 330 and the transmitter section 340 of thetransceiver circuit 304 are connected to a LIN bus 308. The impedance ofthe LIN bus is characterized by a resistor, “Rbus,” which corresponds toan external termination, such as 1 kΩ master termination and a lumpedinternal slave termination, connected in series with a diode, D1, and acapacitor, “Cbus,” which corresponds to parasitic capacitance and othercapacitance (e.g., external decoupling capacitance). The impedance ofthe LIN bus depends on the number of communications devices and thelength of the bus line. Transceiver circuits that are attached to theLIN bus can be switched on and off at any time, thereby changing theresistance of the resistor, Rbus, and the capacitance of the capacitor,Cbus.

The receiver section 330 includes a voltage comparator 332, which may bean error amplifier, and a low-pass filter 334. The voltage comparator isconnected to an output terminal 336, from which a data signal, “RxD,”received from the LIN bus 308, is transmitted to the microcontroller 110(shown in FIG. 1) or other device. The low-pass filter is connected tothe transmitter section and to the LIN bus. The low-pass filter is usedto protect the voltage comparator 332, at which the received signal,RxD, is generated. The receiver section can be implemented as a standardLIN receiver.

The transmitter section 340 includes an output stage or a driving stage342, an error amplifier or operational amplifier (op-amp) 344, a waveshaping circuit or a waveform generator 346, a tunable low-pass filter316, and a control circuit 318. The tunable low-pass filter, the erroramplifier and the driving stage form a feedback loop 314. Thetransmitter section is connected to an input terminal 338, from which adata signal, “TxD,” is received from the microcontroller 110 (shown inFIG. 1) or other device.

The output stage 342 includes a transistor, “M0,” which can be used as avoltage-controlled current source or resistor, diodes, “D2,” “D3,” and apull-up resistor, R_(p). In some embodiments, the pull-up resistor,R_(p), has a resistance value of 30 kΩ.

The waveform generator 346 is configured to generate an output signal inresponse to an input signal and a supply voltage, “Vbat,” which may be abattery voltage. In some embodiments, a waveform shape of an outputsignal of the transceiver circuit 304 to the LIN bus 308 is within therequirements of the LIN specifications in the presence of the RFdisturbance and load impedance variations on the LIN bus.

The error amplifier 344 has a positive input terminal 352, a negativeinput terminal 354, and an output terminal 356. The positive inputterminal is connected to the tunable low-pass filter 316, the negativeinput terminal is connected to the waveform generator 346, and theoutput terminal is connected to the transistor, “M0.”

The control circuit 318 includes a high-pass (HF) filter 348 and anRF-to-Direct Current (DC) converter 350. The control circuit isconfigured to detect the presence of a high-frequency (HF) disturbanceon the LIN bus 308 and to tune the bandwidth of the low-pass filter 316.The high-pass filter is connected to the LIN bus and is configured tofilter the signal received from the LIN bus. The RF-to-DC converter isconnected to the high-pass filter and is configured to detect thepresence of an HF disturbance on the LIN bus based on the filteredsignal from the high-pass filter and to generate a control signal,“Vtune,” to control the bandwidth of the tunable low-pass filter.

In the embodiment depicted in FIG. 3, the transceiver circuit 304 is acontinuous-time feedback transceiver that uses adaptive filtering toachieve low EM emission and high EM immunity. For example, thecontinuous-time feedback from the LIN bus 308 helps to optimize or adaptthe driving voltage of the output transistor, M0, which reduces the areaoverhead of the output transistor, M0. In addition, although thetransceiver circuit is compatible with a cascaded output stage, thetransceiver circuit does not require a cascaded output stage to maintainlow EM emission and high EM immunity.

In an example of the operation of the transceiver circuit 304, LIN busload variations are compensated for by the continuous-time feedback loop314, allowing optimum waveshaping and reducing EM emission. The high EMimmunity is achieved by changing the bandwidth of the feedback loop(i.e., the bandwidth of the low-pass filter 316) based on the amplitudeof HF disturbance detected on the LIN bus 308. Consequently, thetransceiver circuit is protected against HF disturbances on the LIN bus.

In some embodiments, the continuous-time bus feedback loop 314 can beimplemented using a low-pass filter, a resistive divider and an erroramplifier. FIG. 4 depicts an embodiment of the transceiver circuit 304depicted in FIG. 3 that includes a continuous-time bus feedback loop 414having a low-pass filter 416, a resistive divider 460 and an erroramplifier 444. In the embodiment depicted in FIG. 4, a transceivercircuit 404 includes a receiver section 430 and a transmitter section440 that are connected to a LIN bus 408. The impedance of the LIN bus ischaracterized by a resistor, “Rbus,” which corresponds to an externaltermination, such as 1 kΩ master termination and a lumped internal slavetermination, connected in series with a diode, D1, and a capacitor,“Cbus,” which corresponds to parasitic capacitance and other capacitance(e.g., external decoupling capacitance). A voltage source 480 with avoltage, “V_(HF),” may be connected to the LIN bus to conduct EMimmunity tests. The transceiver circuit depicted in FIG. 4 is onepossible embodiment of the transceiver circuit depicted in FIG. 3.However, the transceiver circuit depicted in FIG. 3 is not limited tothe embodiment shown in FIG. 4.

The receiver section 430 of the transceiver circuit 404 includes avoltage comparator 432, which may be an error amplifier, and a low-passfilter 434. The receiver section is connected to an output terminal 436,from which a data signal, “RxD,” received from the LIN bus 408, istransmitted to the microcontroller 110 (shown in FIG. 1) or otherdevice. The receiver section 430 depicted in FIG. 4 may be similar to orthe same as the receiver section 330 depicted in FIG. 3.

The transmitter section 440 of the transceiver circuit 404 includes anoutput stage or a driving stage 442, the resistive divider 460, theerror amplifier 444, a wave shaping circuit or a waveform generator 446,a tunable low-pass filter 416, and a control circuit 418. Thetransmitter section is connected to an input terminal 438, from which adata signal, “TxD,” is received from the microcontroller 110 (shown inFIG. 1) or other device.

The output stage 442 includes a transistor, “M0,” which can be used as avoltage-controlled current source or resistor, diodes, “D2,” “D3,” and apull-up resistor, R_(p). In some embodiments, the pull-up resistor,R_(p), has a resistance value of 30 kΩ.

The resistive divider 460 is connected to the LIN bus 408 and to apositive/non-inverting input terminal 452 of the error amplifier 444.The resistive divider has a division factor, “X,” where X is a positiveinteger. The bus voltage, “Vbus,” can be expressed as:(1)where Vin represents the voltage of the signal that is fed to thepositive input terminal 452 of the error amplifier, and X represents thedivision factor of the resistive divider. The resistive divider canfeedback the bus signal with an appropriate amplitude for the erroramplifier.

In the embodiment depicted in FIG. 4, the error amplifier 444 includesthe positive input terminal 452, a negative input terminal 454, and anoutput terminal 456. The positive input terminal is connected to thetunable low-pass filter 416, the negative input terminal is connected tothe waveform generator 446, and the output terminal is connected to thetransistor, “M0.”

The waveform generator 446 is configured to generate an output signal inresponse to an input signal and a supply voltage, “Vbat,” which may be abattery voltage. In some embodiments, a waveform shape of an outputsignal of the transceiver circuit 404 to the LIN bus 408 is within therequirements of the LIN specifications in the presence of the RFdisturbance and load impedance variations on the LIN bus.

The control circuit 418 includes a number of parallel circuits 470. Eachof the parallel circuits 470 includes a high-pass filter 450 with aunique division factor, an RF-to-DC converter 448 connected to thehigh-pass filter and an error amplifier or operational amplifier(op-amp) 472 connected to the RF-to-DC converter and a referencevoltage, “Vref.” Each HF filter forms a capacitive divider (with adivision factor of 1/(y1+1), 1/(y2+1), 1/(y(n−1)+1) or 1/(y(n)+1), wheren is a positive integer). By changing the division factor (1/(y1+1),1/(y2+1), 1/(y(n−1)+1) or 1/(y(n)+1)) of a capacitive divider, differentHF amplitudes on the LIN bus 408 can be detected, which are used toadjust the bandwidth of the tunable low-pass filter 416.

The tunable low-pass filter 416 includes a number of capacitors (c1, c2,cn-1, cn), where n is a positive integer. The low-pass filter isconfigured to have an adjustable bandwidth to protect the erroramplifier 444 from RF disturbances on the LIN bus 408, which isimportant to achieve high EM Immunity. Upon detecting an HF disturbancesignal on the LIN bus 408, capacitors (c1, c2, cn-1, cn, where n is apositive integer) are connected in the feedback loop 414 using a set oftuning signals, Vtune<0:n>, to form the low-pass filter 416 togetherwith the resistive divider. FIG. 5 is a graph of tuning signal versusthe amplitude of an HF LIN bus disturbance of the transceiver circuit404 depicted in FIG. 4. As shown in FIG. 5, signals in the set of tuningsignals, Vtune<0:n>, are set to high when the HF disturbance amplitudeincreases.

Returning to FIG. 4, the closed-loop LIN transmitter section 440 of thetransceiver circuit 404 can allow the transceiver circuit to have a lowEM emission and can compensate for load variations on the LIN bus 408.FIG. 6 is a graph of a signal voltage that illustrates transmissions ofbits from the transceiver circuit depicted in FIG. 4 under differentbus-load conditions. In a first bus-load condition, the LIN bus has aresistance of 1142 and a capacitance of 4.7nf. In a second bus-loadcondition, the LIN bus has a resistance of 1 kΩ and a capacitance of 1nf. As shown in FIG. 6, the transceiver circuit 404 can cope withdifferent bus-load conditions.

FIG. 7 is a graph of an EM Immunity simulation of the transceivercircuit 404 depicted in FIG. 4. In the simulation diagram shown in FIG.7, the transmission of some bits is simulated while a sinewave of 10Vpeak-to-peak at 1 MHz is injected onto the LIN bus 408. In particular,FIG. 7 shows a waveform of a reference LIN signal when no HFdisturbances (VRF=0) are applied and a waveform of a LIN signal(VRF=10Vpp) while a sinewave is applied. Consequently, a high-frequency(HF) signal is present on the LIN bus while the average amplitude swingsfrom recessive to dominant states. The comparison with a LIN signaltransmitted without the injection of HF disturbance shows that theaverage recessive voltage, dominant voltage and the slew rate are keptunder control using the HF detection that sets an appropriatefeedback-loop bandwidth.

FIG. 8 is a graph representing the bit time of a received signal of thetransceiver circuit 404 depicted in FIG. 4 during an EM Immunitysimulation. In the diagram shown in FIG. 8, the received signal, RxD,relative to 50 μs is plotted for HF amplitudes up to 20V(40Vpeak-to-peak) and an error that is calculated relative to 50 us (ason TxD) is also plotted. In the graph depicted in FIG. 8, the jitter ofthe signal RxD is limited, while a maximum error is lower than themaximum error allowed. Consequently, the transceiver circuit 404depicted in FIG. 4 can achieve a lower EM emission than a conventionalopen-loop approach and good EM immunity.

FIG. 9 is a process flow diagram of a method for operating a transceivercircuit in accordance with an embodiment of the invention. Thetransceiver circuit may be similar to or the same as the transceivercircuit 104 depicted in FIG. 1, the transceiver circuit 204 or 224depicted in FIG. 2, the transceiver circuit 304 depicted in FIG. 3,and/or the transceiver circuit 404 depicted in FIG. 4. At block 902, anRF disturbance on a bus connected to the transceiver circuit isdetected. At block 904, the bandwidth of a tunable low-pass filter ofthe transceiver circuit is controlled in response to detection of the RFdisturbance on the bus.

FIG. 10 is a process flow diagram of a method for operating atransceiver circuit in accordance with another embodiment of theinvention. The transceiver circuit may be similar to or the same as thetransceiver circuit 104 depicted in FIG. 1, the transceiver circuit 204or 224 depicted in FIG. 2, the transceiver circuit 304 depicted in FIG.3, and/or the transceiver circuit 404 depicted in FIG. 4. At step 1002,a low-pass filter of the transceiver circuit is set to full bandwidth.At step 1004, a LIN signal is transmitted (e.g., as the data signal,RxD, through the output terminal 436). At step 1006, a detection of highfrequency (HF) disturbance of the LIN signal is performed. If HFdisturbance is detected, the bandwidth of the low-pass filter of thetransceiver circuit is controlled at step 1008, a LIN signal withlimited jitter is transmitted (e.g., as the data signal, RxD, throughthe output terminal 436) at step 1010, and the method goes back to step1006. If HF disturbance is not detected, the method goes back to step1002.

Although the operations of the method herein are shown and described ina particular order, the order of the operations of the method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

In addition, although specific embodiments of the invention that havebeen described or depicted include several components described ordepicted herein, other embodiments of the invention may include fewer ormore components to implement less or more features.

Furthermore, although specific embodiments of the invention have beendescribed and depicted, the invention is not to be limited to thespecific forms or arrangements of parts so described and depicted. Thescope of the invention is to be defined by the claims appended heretoand their equivalents.

What is claimed is:
 1. A transceiver circuit, the transceiver circuitcomprising: a feedback loop connected to a bus, wherein the feedbackloop comprises a tunable low-pass filter; and a control circuitconnected to the bus and configured to: detect a radio frequency (RF)disturbance on the bus; and control the bandwidth of the tunablelow-pass filter in response to detection of the RF disturbance on thebus.
 2. The transceiver circuit of claim 1, wherein the control circuitis further configured to change the bandwidth of the tunable low-passfilter based on an amplitude of the RF disturbance on the bus.
 3. Thetransceiver circuit of claim 1, wherein the control circuit comprises: ahigh-pass filter connected to the bus; and an RF-to-Direct Current (DC)converter connected to the high-pass filter and configured to generate acontrol signal to control the bandwidth of the tunable low-pass filter.4. The transceiver circuit of claim 3, wherein the high-pass filtercomprises a capacitive divider.
 5. The transceiver circuit of claim 1,wherein the control circuit comprises a plurality of parallel circuits,and wherein each of the parallel circuits comprises: a high-pass filterwith a unique division factor; an RF-to-Direct Current (DC) converterconnected to the high-pass filter; and an error amplifier connected tothe RF-to-DC converter and a reference voltage.
 6. The transceivercircuit of claim 5, wherein the tunable low-pass filter comprises aresistive divider and selectable capacitors.
 7. The transceiver circuitof claim 1, wherein the control circuit comprises a plurality ofhigh-pass filters with different division factors.
 8. The transceivercircuit of claim 1, wherein the transceiver circuit further comprises: awaveform generator configured to generate an output signal in responseto an input signal and a supply voltage.
 9. The transceiver circuit ofclaim 8, wherein the feedback loop further comprises: an error amplifierwith a first input terminal and a second input terminal, wherein thefirst input terminal is connected to the tunable low-pass filter, andwherein the second input terminal is connected to the waveformgenerator.
 10. The transceiver circuit of claim 9, wherein the bus is asingle-ended bus.
 11. The transceiver circuit of claim 9, wherein thetransceiver circuit further comprises: an output stage configured to bedriven by the feedback loop.
 12. The transceiver circuit of claim 11,wherein the output stage comprises: a transistor connected to an outputterminal of the error amplifier; a resistor; and at least one diode. 13.The transceiver circuit of claim 11, wherein the transceiver circuitcomprises a receiver section and a transmitter section, and wherein thetransmitter section comprises the feedback loop, the control circuit,the waveform generator, and the output stage.
 14. The transceivercircuit of claim 1, wherein the transceiver circuit comprises a receiversection connected to the bus, and wherein a jitter of an output signalof the receiver section is limited in response to an adjustment of thebandwidth of the tunable low-pass filter.
 15. A method for operating atransceiver circuit, the method comprising: detecting a radio frequency(RF) disturbance on a bus connected to the transceiver circuit; andcontrolling the bandwidth of a tunable low-pass filter of thetransceiver circuit in response to detection of the RF disturbance onthe bus.
 16. The method of claim 15, wherein the bus is a single-endedbus, and wherein controlling the bandwidth of the tunable low-passfilter of the transceiver circuit in response to detection of the RFdisturbance on the single-ended bus comprises changing the bandwidth ofthe tunable low-pass filter based on an amplitude of the RF disturbanceon the single-ended bus.
 17. A transceiver circuit, the transceivercircuit comprising a receiver section and a transmitter section, thetransmitter section comprises: a feedback loop connected to asingle-ended bus, wherein the feedback loop comprises a tunable low-passfilter and an error amplifier; and a control circuit connected to thesingle-ended bus and configured to: detect a radio frequency (RF)disturbance on the single-ended bus; and control the bandwidth of thetunable low-pass filter in response to detection of the RF disturbanceon the single-ended bus.
 18. The transceiver circuit of claim 17,wherein the transmitter section further comprises: a waveform generatorconfigured to generate an output signal in response to an input signaland a supply voltage; and an output stage configured to be driven by thefeedback loop.
 19. The transceiver circuit of claim 18, wherein thecontrol circuit comprises: a high-pass filter connected to thesingle-ended bus; and an RF-to-Direct Current (DC) converter connectedto the high-pass filter and configured to generate a control signal tocontrol the bandwidth of the tunable low-pass filter, and wherein thetunable low-pass filter comprises: a plurality of capacitors that areconnected in parallel with each other; and a resistive divider connectedto the capacitors.
 20. The transceiver circuit of claim 17, wherein thesingle-ended bus is a Local Interconnect Network (LIN) bus.